It has been shown that wildlife crossings — overpasses and underpasses combined with fencing — reduce those accidents in which vehicles collide with deer-sized and larger animals by an average of 87%, according to an article appearing in ITE Journal (the journal of the Institute of Transportation Engineers). The article says there are many areas in the United States and Canada where the benefits of installing such wildlife crossings would be greater than the costs of collisions between vehicles and large animals like deer, elk, and moose.

Collisions between wild animals and commercials trucks are especially common because truckers often choose to drive at night to avoid congestion.

This truck has been retrofitted with a grill guard to protect it in a collision with wild animals.

The Regional Transportation Authority (RTA) Wildlife Linkages Group of Tucson, Arizona plans to meet on August 14 to discuss several wildlife crossing projects planned for Pima County, Arizona, as Bud Foster writes for Tucson News Now. In 2006, Tucson voters passed the Regional Transportation Authority (RTA), which allocated $45 million for wildlife crossings, Foster writes. That sum covers the design and construction of wildlife crossings in future roadways, as well as the retrofitting of existing roads with wildlife crossing improvements, according to RTA.

In one project that will cost $2.5 million, the RTA in 2016 will add five box culverts, from six to eight feet high, to Tangerine Road, Foster reports. He notes that Tangerine Road is one of the most important wildlife corridors in Arizona. There were 5,132 animals killed on a six-mile section of the road during one five-month period, according to a 2010 study by the Arizona Game and Fish, Foster writes.

Additionally, in a $7 million project, the RTA plans on building three underground corridors and two bridges along Highway 86 near Kitt Peak, Foster writes. Highway 86 is another important wildlife corridor, featuring deer, elk, cougars, javelinas, coyotes, and jackrabbits.

In an article appearing on Atlas Obscura, Eric Grundhauser writes that wildlife crossings resemble those that people might walk or drive on, the main difference being that the wildlife crossings are draped in foliage and ground covering and thus look like part of the landscape. Such “re-greened bridges” are especially useful for larger animals, he writes. But there are also special crossings created for smaller animals. One such example is the Toad Tunnel in Davis, California. A six-inch wide ecoduct built to keep frogs from getting run over on the road, the Toad Tunnel did not attract frogs at first, but they eventually began using it, Grundhauser writes.

In response to the question of how animals know how to use the crossings, RTA writes that specially designed fencing is installed on both sides of a crossing to “funnel” wildlife towards it. The fencing is eight feet high to prevent animals such as deer from jumping over it, and is made of fine mesh panels to prevent small mammals, snakes, and lizards from going through it onto the road. The fencing is buried six inches below ground so that animals will have a hard time burrowing under it, RTA writes.

Although the crossings are designed to attract animals, one comment to the Tucson News Now article raises an important question. The commenter, Lee Ann Tinnin, of Tucson, Arizona, writes: “Just a question, who is going to tell the animals to only cross there? :-)”